Our research is concerned with the control of organelle development. In combination with high-resolution density gradient centrifugation to obtain large quantities of pure, intact chloroplasts and mitochondria, we have been employing SDS-polyacrylamide gel electrophoresis as a probe in characterizing the different protein components of the organelles, e.g., membranes, soluble phase and ribosomes. We are now following the sequence of changes of specific proteins during chloroplast development. At the same time, we will be looking at the proteins of bovine fetal and adult mitochondria to see if there are qualitative differences to be found among these. We also plan to initiate studies on how cytoplasmically derived proteins are incorporated into organelle structures by testing for the incorporation of radioactively-labeled cytoplasmic proteins into isolated chloroplasts.